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readelf.c

/*
 * Copyright (c) Christos Zoulas 2003.
 * All Rights Reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice immediately at the beginning of the file, without modification,
 *    this list of conditions, and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *  
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
#include "file.h"

#ifdef BUILTIN_ELF
#include <string.h>
#include <ctype.h>
#include <stdlib.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#include "readelf.h"

#ifndef lint
FILE_RCSID("@(#)$Id: readelf.c,v 1.54 2006/01/13 00:45:21 christos Exp $")
#endif

#ifdef      ELFCORE
private int dophn_core(struct magic_set *, int, int, int, off_t, int, size_t);
#endif
private int dophn_exec(struct magic_set *, int, int, int, off_t, int, size_t);
private int doshn(struct magic_set *, int, int, int, off_t, int, size_t);
private size_t donote(struct magic_set *, unsigned char *, size_t, size_t, int,
    int, size_t, int *);

#define     ELF_ALIGN(a)      ((((a) + align - 1) / align) * align)

#define isquote(c) (strchr("'\"`", (c)) != NULL)

private uint16_t getu16(int, uint16_t);
private uint32_t getu32(int, uint32_t);
private uint64_t getu64(int, uint64_t);

private uint16_t
getu16(int swap, uint16_t value)
{
      union {
            uint16_t ui;
            char c[2];
      } retval, tmpval;

      if (swap) {
            tmpval.ui = value;

            retval.c[0] = tmpval.c[1];
            retval.c[1] = tmpval.c[0];
            
            return retval.ui;
      } else
            return value;
}

private uint32_t
getu32(int swap, uint32_t value)
{
      union {
            uint32_t ui;
            char c[4];
      } retval, tmpval;

      if (swap) {
            tmpval.ui = value;

            retval.c[0] = tmpval.c[3];
            retval.c[1] = tmpval.c[2];
            retval.c[2] = tmpval.c[1];
            retval.c[3] = tmpval.c[0];
            
            return retval.ui;
      } else
            return value;
}

private uint64_t
getu64(int swap, uint64_t value)
{
      union {
            uint64_t ui;
            char c[8];
      } retval, tmpval;

      if (swap) {
            tmpval.ui = value;

            retval.c[0] = tmpval.c[7];
            retval.c[1] = tmpval.c[6];
            retval.c[2] = tmpval.c[5];
            retval.c[3] = tmpval.c[4];
            retval.c[4] = tmpval.c[3];
            retval.c[5] = tmpval.c[2];
            retval.c[6] = tmpval.c[1];
            retval.c[7] = tmpval.c[0];
            
            return retval.ui;
      } else
            return value;
}

#ifdef USE_ARRAY_FOR_64BIT_TYPES
# define elf_getu64(swap, array) \
      ((swap ? ((uint64_t)getu32(swap, array[0])) << 32 : getu32(swap, array[0])) + \
       (swap ? getu32(swap, array[1]) : ((uint64_t)getu32(swap, array[1]) << 32)))
#else
# define elf_getu64(swap, value) getu64(swap, value)
#endif

#define xsh_addr  (class == ELFCLASS32          \
                   ? (void *) &sh32       \
                   : (void *) &sh64)
#define xsh_sizeof      (class == ELFCLASS32          \
                   ? sizeof sh32                \
                   : sizeof sh64)
#define xsh_size  (class == ELFCLASS32          \
                   ? getu32(swap, sh32.sh_size) \
                   : getu64(swap, sh64.sh_size))
#define xsh_offset      (class == ELFCLASS32          \
                   ? getu32(swap, sh32.sh_offset)     \
                   : getu64(swap, sh64.sh_offset))
#define xsh_type  (class == ELFCLASS32          \
                   ? getu32(swap, sh32.sh_type) \
                   : getu32(swap, sh64.sh_type))
#define xph_addr  (class == ELFCLASS32          \
                   ? (void *) &ph32       \
                   : (void *) &ph64)
#define xph_sizeof      (class == ELFCLASS32          \
                   ? sizeof ph32                \
                   : sizeof ph64)
#define xph_type  (class == ELFCLASS32          \
                   ? getu32(swap, ph32.p_type)  \
                   : getu32(swap, ph64.p_type))
#define xph_offset      (class == ELFCLASS32          \
                   ? getu32(swap, ph32.p_offset)      \
                   : getu64(swap, ph64.p_offset))
#define xph_align (size_t)((class == ELFCLASS32 \
                   ? (off_t) (ph32.p_align ?    \
                      getu32(swap, ph32.p_align) : 4) \
                   : (off_t) (ph64.p_align ?    \
                      getu64(swap, ph64.p_align) : 4)))
#define xph_filesz      (size_t)((class == ELFCLASS32 \
                   ? getu32(swap, ph32.p_filesz)      \
                   : getu64(swap, ph64.p_filesz)))
#define xnh_addr  (class == ELFCLASS32          \
                   ? (void *) &nh32       \
                   : (void *) &nh64)
#define xph_memsz (size_t)((class == ELFCLASS32 \
                   ? getu32(swap, ph32.p_memsz) \
                   : getu64(swap, ph64.p_memsz)))
#define xnh_sizeof      (class == ELFCLASS32          \
                   ? sizeof nh32                \
                   : sizeof nh64)
#define xnh_type  (class == ELFCLASS32          \
                   ? getu32(swap, nh32.n_type)  \
                   : getu32(swap, nh64.n_type))
#define xnh_namesz      (class == ELFCLASS32          \
                   ? getu32(swap, nh32.n_namesz)      \
                   : getu32(swap, nh64.n_namesz))
#define xnh_descsz      (class == ELFCLASS32          \
                   ? getu32(swap, nh32.n_descsz)      \
                   : getu32(swap, nh64.n_descsz))
#define prpsoffsets(i)  (class == ELFCLASS32          \
                   ? prpsoffsets32[i]           \
                   : prpsoffsets64[i])

#ifdef ELFCORE
size_t      prpsoffsets32[] = {
      8,          /* FreeBSD */
      28,         /* Linux 2.0.36 */
      32,         /* Linux (I forget which kernel version) */
      84,         /* SunOS 5.x */
};

size_t      prpsoffsets64[] = {
      16,         /* FreeBSD, 64-bit */
      40,             /* Linux (tested on core from 2.4.x) */
       120,       /* SunOS 5.x, 64-bit */
};

#define     NOFFSETS32  (sizeof prpsoffsets32 / sizeof prpsoffsets32[0])
#define NOFFSETS64      (sizeof prpsoffsets64 / sizeof prpsoffsets64[0])

#define NOFFSETS  (class == ELFCLASS32 ? NOFFSETS32 : NOFFSETS64)

/*
 * Look through the program headers of an executable image, searching
 * for a PT_NOTE section of type NT_PRPSINFO, with a name "CORE" or
 * "FreeBSD"; if one is found, try looking in various places in its
 * contents for a 16-character string containing only printable
 * characters - if found, that string should be the name of the program
 * that dropped core.  Note: right after that 16-character string is,
 * at least in SunOS 5.x (and possibly other SVR4-flavored systems) and
 * Linux, a longer string (80 characters, in 5.x, probably other
 * SVR4-flavored systems, and Linux) containing the start of the
 * command line for that program.
 *
 * The signal number probably appears in a section of type NT_PRSTATUS,
 * but that's also rather OS-dependent, in ways that are harder to
 * dissect with heuristics, so I'm not bothering with the signal number.
 * (I suppose the signal number could be of interest in situations where
 * you don't have the binary of the program that dropped core; if you
 * *do* have that binary, the debugger will probably tell you what
 * signal it was.)
 */

#define     OS_STYLE_SVR4           0
#define     OS_STYLE_FREEBSD  1
#define     OS_STYLE_NETBSD         2

private const char *os_style_names[] = {
      "SVR4",
      "FreeBSD",
      "NetBSD",
};

#define FLAGS_DID_CORE        1

private int
dophn_core(struct magic_set *ms, int class, int swap, int fd, off_t off,
    int num, size_t size)
{
      Elf32_Phdr ph32;
      Elf64_Phdr ph64;
      size_t offset;
      unsigned char nbuf[BUFSIZ];
      ssize_t bufsize;
      int flags = 0;

      if (size != xph_sizeof) {
            if (file_printf(ms, ", corrupted program header size") == -1)
                  return -1;
            return 0;
      }

      /*
       * Loop through all the program headers.
       */
      for ( ; num; num--) {
            if (lseek(fd, off, SEEK_SET) == (off_t)-1) {
                  file_badseek(ms);
                  return -1;
            }
            if (read(fd, xph_addr, xph_sizeof) == -1) {
                  file_badread(ms);
                  return -1;
            }
            off += size;
            if (xph_type != PT_NOTE)
                  continue;

            /*
             * This is a PT_NOTE section; loop through all the notes
             * in the section.
             */
            if (lseek(fd, (off_t)xph_offset, SEEK_SET) == (off_t)-1) {
                  file_badseek(ms);
                  return -1;
            }
            bufsize = read(fd, nbuf,
                ((xph_filesz < sizeof(nbuf)) ? xph_filesz : sizeof(nbuf)));
            if (bufsize == -1) {
                  file_badread(ms);
                  return -1;
            }
            offset = 0;
            for (;;) {
                  if (offset >= (size_t)bufsize)
                        break;
                  offset = donote(ms, nbuf, offset, (size_t)bufsize,
                      class, swap, 4, &flags);
                  if (offset == 0)
                        break;

            }
      }
      return 0;
}
#endif

private size_t
donote(struct magic_set *ms, unsigned char *nbuf, size_t offset, size_t size,
    int class, int swap, size_t align, int *flags)
{
      Elf32_Nhdr nh32;
      Elf64_Nhdr nh64;
      size_t noff, doff;
#ifdef ELFCORE
      int os_style = -1;
#endif
      uint32_t namesz, descsz;

      (void)memcpy(xnh_addr, &nbuf[offset], xnh_sizeof);
      offset += xnh_sizeof;

      namesz = xnh_namesz;
      descsz = xnh_descsz;
      if ((namesz == 0) && (descsz == 0)) {
            /*
             * We're out of note headers.
             */
            return offset;
      }

      if (namesz & 0x80000000) {
          (void)file_printf(ms, ", bad note name size 0x%lx",
            (unsigned long)namesz);
          return offset;
      }

      if (descsz & 0x80000000) {
          (void)file_printf(ms, ", bad note description size 0x%lx",
            (unsigned long)descsz);
          return offset;
      }


      noff = offset;
      doff = ELF_ALIGN(offset + namesz);

      if (offset + namesz > size) {
            /*
             * We're past the end of the buffer.
             */
            return doff;
      }

      offset = ELF_ALIGN(doff + descsz);
      if (doff + descsz > size) {
            return offset;
      }

      if (namesz == 4 && strcmp((char *)&nbuf[noff], "GNU") == 0 &&
          xnh_type == NT_GNU_VERSION && descsz == 16) {
            uint32_t desc[4];
            (void)memcpy(desc, &nbuf[doff], sizeof(desc));

            if (file_printf(ms, ", for GNU/") == -1)
                  return size;
            switch (getu32(swap, desc[0])) {
            case GNU_OS_LINUX:
                  if (file_printf(ms, "Linux") == -1)
                        return size;
                  break;
            case GNU_OS_HURD:
                  if (file_printf(ms, "Hurd") == -1)
                        return size;
                  break;
            case GNU_OS_SOLARIS:
                  if (file_printf(ms, "Solaris") == -1)
                        return size;
                  break;
            default:
                  if (file_printf(ms, "<unknown>") == -1)
                        return size; 
            }
            if (file_printf(ms, " %d.%d.%d", getu32(swap, desc[1]),
                getu32(swap, desc[2]), getu32(swap, desc[3])) == -1)
                  return size;
            return size;
      }

      if (namesz == 7 && strcmp((char *)&nbuf[noff], "NetBSD") == 0 &&
          xnh_type == NT_NETBSD_VERSION && descsz == 4) {
            uint32_t desc;
            (void)memcpy(&desc, &nbuf[doff], sizeof(desc));
            desc = getu32(swap, desc);

            if (file_printf(ms, ", for NetBSD") == -1)
                  return size;
            /*
             * The version number used to be stuck as 199905, and was thus
             * basically content-free.  Newer versions of NetBSD have fixed
             * this and now use the encoding of __NetBSD_Version__:
             *
             *    MMmmrrpp00
             *
             * M = major version
             * m = minor version
             * r = release ["",A-Z,Z[A-Z] but numeric]
             * p = patchlevel
             */
            if (desc > 100000000U) {
                  u_int ver_patch = (desc / 100) % 100;
                  u_int ver_rel = (desc / 10000) % 100;
                  u_int ver_min = (desc / 1000000) % 100;
                  u_int ver_maj = desc / 100000000;

                  if (file_printf(ms, " %u.%u", ver_maj, ver_min) == -1)
                        return size;
                  if (ver_rel == 0 && ver_patch != 0) {
                        if (file_printf(ms, ".%u", ver_patch) == -1)
                              return size;
                  } else if (ver_rel != 0) {
                        while (ver_rel > 26) {
                              file_printf(ms, "Z");
                              ver_rel -= 26;
                        }
                        file_printf(ms, "%c", 'A' + ver_rel - 1);
                  }
            }
            return size;
      }

      if (namesz == 8 && strcmp((char *)&nbuf[noff], "FreeBSD") == 0 &&
          xnh_type == NT_FREEBSD_VERSION && descsz == 4) {
            uint32_t desc;
            (void)memcpy(&desc, &nbuf[doff], sizeof(desc));
            desc = getu32(swap, desc);
            if (file_printf(ms, ", for FreeBSD") == -1)
                  return size;

            /*
             * Contents is __FreeBSD_version, whose relation to OS
             * versions is defined by a huge table in the Porter's
             * Handbook.  This is the general scheme:
             * 
             * Releases:
             *    Mmp000 (before 4.10)
             *    Mmi0p0 (before 5.0)
             *    Mmm0p0
             * 
             * Development branches:
             *    Mmpxxx (before 4.6)
             *    Mmp1xx (before 4.10)
             *    Mmi1xx (before 5.0)
             *    M000xx (pre-M.0)
             *    Mmm1xx
             * 
             * M = major version
             * m = minor version
             * i = minor version increment (491000 -> 4.10)
             * p = patchlevel
             * x = revision
             * 
             * The first release of FreeBSD to use ELF by default
             * was version 3.0.
             */
            if (desc == 460002) {
                  if (file_printf(ms, " 4.6.2") == -1)
                        return size;
            } else if (desc < 460100) {
                  if (file_printf(ms, " %d.%d", desc / 100000,
                      desc / 10000 % 10) == -1)
                        return size;
                  if (desc / 1000 % 10 > 0)
                        if (file_printf(ms, ".%d", desc / 1000 % 10)
                            == -1)
                              return size;
                  if ((desc % 1000 > 0) || (desc % 100000 == 0))
                        if (file_printf(ms, " (%d)", desc) == -1)
                              return size;
            } else if (desc < 500000) {
                  if (file_printf(ms, " %d.%d", desc / 100000,
                      desc / 10000 % 10 + desc / 1000 % 10) == -1)
                        return size;
                  if (desc / 100 % 10 > 0) {
                        if (file_printf(ms, " (%d)", desc) == -1)
                              return size;
                  } else if (desc / 10 % 10 > 0) {
                        if (file_printf(ms, ".%d", desc / 10 % 10)
                            == -1)
                              return size;
                  }
            } else {
                  if (file_printf(ms, " %d.%d", desc / 100000,
                      desc / 1000 % 100) == -1)
                        return size;
                  if ((desc / 100 % 10 > 0) ||
                      (desc % 100000 / 100 == 0)) {
                        if (file_printf(ms, " (%d)", desc) == -1)
                              return size;
                  } else if (desc / 10 % 10 > 0) {
                        if (file_printf(ms, ".%d", desc / 10 % 10)
                            == -1)
                              return size;
                  }
            }
            return size;
      }

      if (namesz == 8 && strcmp((char *)&nbuf[noff], "OpenBSD") == 0 &&
          xnh_type == NT_OPENBSD_VERSION && descsz == 4) {
            if (file_printf(ms, ", for OpenBSD") == -1)
                  return size;
            /* Content of note is always 0 */
            return size;
      }

      if (namesz == 10 && strcmp((char *)&nbuf[noff], "DragonFly") == 0 &&
          xnh_type == NT_DRAGONFLY_VERSION && descsz == 4) {
            uint32_t desc;
            if (file_printf(ms, ", for DragonFly") == -1)
                  return size;
            (void)memcpy(&desc, &nbuf[doff], sizeof(desc));
            desc = getu32(swap, desc);
            if (file_printf(ms, " %d.%d.%d", desc / 100000,
                desc / 10000 % 10, desc % 10000) == -1)
                  return size;
            return size;
      }

      /*
       * Sigh.  The 2.0.36 kernel in Debian 2.1, at
       * least, doesn't correctly implement name
       * sections, in core dumps, as specified by
       * the "Program Linking" section of "UNIX(R) System
       * V Release 4 Programmer's Guide: ANSI C and
       * Programming Support Tools", because my copy
       * clearly says "The first 'namesz' bytes in 'name'
       * contain a *null-terminated* [emphasis mine]
       * character representation of the entry's owner
       * or originator", but the 2.0.36 kernel code
       * doesn't include the terminating null in the
       * name....
       */
      if ((namesz == 4 && strncmp((char *)&nbuf[noff], "CORE", 4) == 0) ||
          (namesz == 5 && strcmp((char *)&nbuf[noff], "CORE") == 0)) {
            os_style = OS_STYLE_SVR4;
      } 

      if ((namesz == 8 && strcmp((char *)&nbuf[noff], "FreeBSD") == 0)) {
            os_style = OS_STYLE_FREEBSD;
      }

      if ((namesz >= 11 && strncmp((char *)&nbuf[noff], "NetBSD-CORE", 11)
          == 0)) {
            os_style = OS_STYLE_NETBSD;
      }

#ifdef ELFCORE
      if (os_style != -1) {
            if ((*flags & FLAGS_DID_CORE) == 0) {
                  if (file_printf(ms, ", %s-style",
                      os_style_names[os_style]) == -1)
                        return size;
                  *flags |= FLAGS_DID_CORE;
            }
      }

      switch (os_style) {
      case OS_STYLE_NETBSD:
            if (xnh_type == NT_NETBSD_CORE_PROCINFO) {
                  uint32_t signo;
                  /*
                   * Extract the program name.  It is at
                   * offset 0x7c, and is up to 32-bytes,
                   * including the terminating NUL.
                   */
                  if (file_printf(ms, ", from '%.31s'",
                      &nbuf[doff + 0x7c]) == -1)
                        return size;
                  
                  /*
                   * Extract the signal number.  It is at
                   * offset 0x08.
                   */
                  (void)memcpy(&signo, &nbuf[doff + 0x08],
                      sizeof(signo));
                  if (file_printf(ms, " (signal %u)",
                      getu32(swap, signo)) == -1)
                        return size;
                  return size;
            }
            break;

      default:
            if (xnh_type == NT_PRPSINFO) {
                  size_t i, j;
                  unsigned char c;
                  /*
                   * Extract the program name.  We assume
                   * it to be 16 characters (that's what it
                   * is in SunOS 5.x and Linux).
                   *
                   * Unfortunately, it's at a different offset
                   * in varous OSes, so try multiple offsets.
                   * If the characters aren't all printable,
                   * reject it.
                   */
                  for (i = 0; i < NOFFSETS; i++) {
                        size_t reloffset = prpsoffsets(i);
                        size_t noffset = doff + reloffset;
                        for (j = 0; j < 16; j++, noffset++,
                            reloffset++) {
                              /*
                               * Make sure we're not past
                               * the end of the buffer; if
                               * we are, just give up.
                               */
                              if (noffset >= size)
                                    goto tryanother;

                              /*
                               * Make sure we're not past
                               * the end of the contents;
                               * if we are, this obviously
                               * isn't the right offset.
                               */
                              if (reloffset >= descsz)
                                    goto tryanother;

                              c = nbuf[noffset];
                              if (c == '\0') {
                                    /*
                                     * A '\0' at the
                                     * beginning is
                                     * obviously wrong.
                                     * Any other '\0'
                                     * means we're done.
                                     */
                                    if (j == 0)
                                          goto tryanother;
                                    else
                                          break;
                              } else {
                                    /*
                                     * A nonprintable
                                     * character is also
                                     * wrong.
                                     */
                                    if (!isprint(c) || isquote(c))
                                          goto tryanother;
                              }
                        }
                        /*
                         * Well, that worked.
                         */
                        if (file_printf(ms, ", from '%.16s'",
                            &nbuf[doff + prpsoffsets(i)]) == -1)
                              return size;
                        return size;

                  tryanother:
                        ;
                  }
            }
            break;
      }
#endif
      return offset;
}

private int
doshn(struct magic_set *ms, int class, int swap, int fd, off_t off, int num,
    size_t size)
{
      Elf32_Shdr sh32;
      Elf64_Shdr sh64;
      int stripped = 1;
      int flags = 0;
      void *nbuf;
      off_t noff;

      if (size != xsh_sizeof) {
            if (file_printf(ms, ", corrupted section header size") == -1)
                  return -1;
            return 0;
      }

      if (lseek(fd, off, SEEK_SET) == (off_t)-1) {
            file_badseek(ms);
            return -1;
      }

      for ( ; num; num--) {
            if (read(fd, xsh_addr, xsh_sizeof) == -1) {
                  file_badread(ms);
                  return -1;
            }
            switch (xsh_type) {
            case SHT_SYMTAB:
#if 0
            case SHT_DYNSYM:
#endif
                  stripped = 0;
                  break;
            case SHT_NOTE:
                  if ((off = lseek(fd, (off_t)0, SEEK_CUR)) ==
                      (off_t)-1) {
                        file_badread(ms);
                        return -1;
                  }
                  if ((nbuf = malloc((size_t)xsh_size)) == NULL) {
                        file_error(ms, errno, "Cannot allocate memory"
                            " for note");
                        return -1;
                  }
                  if ((noff = lseek(fd, (off_t)xsh_offset, SEEK_SET)) ==
                      (off_t)-1) {
                        file_badread(ms);
                        free(nbuf);
                        return -1;
                  }
                  if (read(fd, nbuf, (size_t)xsh_size) !=
                      (ssize_t)xsh_size) {
                        free(nbuf);
                        file_badread(ms);
                        return -1;
                  }

                  noff = 0;
                  for (;;) {
                        if (noff >= (size_t)xsh_size)
                              break;
                        noff = donote(ms, nbuf, (size_t)noff,
                            (size_t)xsh_size, class, swap, 4,
                            &flags);
                        if (noff == 0)
                              break;
                  }
                  if ((lseek(fd, off, SEEK_SET)) == (off_t)-1) {
                        free(nbuf);
                        file_badread(ms);
                        return -1;
                  }
                  free(nbuf);
                  break;
            }
      }
      if (file_printf(ms, ", %sstripped", stripped ? "" : "not ") == -1)
            return -1;
      return 0;
}

/*
 * Look through the program headers of an executable image, searching
 * for a PT_INTERP section; if one is found, it's dynamically linked,
 * otherwise it's statically linked.
 */
private int
dophn_exec(struct magic_set *ms, int class, int swap, int fd, off_t off,
    int num, size_t size)
{
      Elf32_Phdr ph32;
      Elf64_Phdr ph64;
      const char *linking_style = "statically";
      const char *shared_libraries = "";
      unsigned char nbuf[BUFSIZ];
      int bufsize;
      size_t offset, align;
      off_t savedoffset;
      int flags = 0;

      if (size != xph_sizeof) {
            if (file_printf(ms, ", corrupted program header size") == -1)
                return -1;
            return 0;
      }
      if (lseek(fd, off, SEEK_SET) == (off_t)-1) {
            file_badseek(ms);
            return -1;
      }

      for ( ; num; num--) {
            if (read(fd, xph_addr, xph_sizeof) == -1) {
                  file_badread(ms);
                  return -1;
            }
            if ((savedoffset = lseek(fd, (off_t)0, SEEK_CUR)) == (off_t)-1) {
                  file_badseek(ms);
                  return -1;
            }

            switch (xph_type) {
            case PT_DYNAMIC:
                  linking_style = "dynamically";
                  break;
            case PT_INTERP:
                  shared_libraries = " (uses shared libs)";
                  break;
            case PT_NOTE:
                  if ((align = xph_align) & 0x80000000) {
                        if (file_printf(ms, 
                            ", invalid note alignment 0x%lx",
                            (unsigned long)align) == -1)
                              return -1;
                        align = 4;
                  }
                  /*
                   * This is a PT_NOTE section; loop through all the notes
                   * in the section.
                   */
                  if (lseek(fd, (off_t)xph_offset, SEEK_SET)
                      == (off_t)-1) {
                        file_badseek(ms);
                        return -1;
                  }
                  bufsize = read(fd, nbuf, ((xph_filesz < sizeof(nbuf)) ?
                      xph_filesz : sizeof(nbuf)));
                  if (bufsize == -1) {
                        file_badread(ms);
                        return -1;
                  }
                  offset = 0;
                  for (;;) {
                        if (offset >= (size_t)bufsize)
                              break;
                        offset = donote(ms, nbuf, offset,
                            (size_t)bufsize, class, swap, align,
                            &flags);
                        if (offset == 0)
                              break;
                  }
                  if (lseek(fd, savedoffset, SEEK_SET) == (off_t)-1) {
                        file_badseek(ms);
                        return -1;
                  }
                  break;
            }
      }
      if (file_printf(ms, ", %s linked%s", linking_style, shared_libraries)
          == -1)
          return -1;
      return 0;
}


protected int
file_tryelf(struct magic_set *ms, int fd, const unsigned char *buf,
    size_t nbytes)
{
      union {
            int32_t l;
            char c[sizeof (int32_t)];
      } u;
      int class;
      int swap;

      /*
       * If we cannot seek, it must be a pipe, socket or fifo.
       */
      if((lseek(fd, (off_t)0, SEEK_SET) == (off_t)-1) && (errno == ESPIPE))
            fd = file_pipe2file(ms, fd, buf, nbytes);

      /*
       * ELF executables have multiple section headers in arbitrary
       * file locations and thus file(1) cannot determine it from easily.
       * Instead we traverse thru all section headers until a symbol table
       * one is found or else the binary is stripped.
       */
      if (buf[EI_MAG0] != ELFMAG0
          || (buf[EI_MAG1] != ELFMAG1 && buf[EI_MAG1] != OLFMAG1)
          || buf[EI_MAG2] != ELFMAG2 || buf[EI_MAG3] != ELFMAG3)
          return 0;


      class = buf[4];

      if (class == ELFCLASS32) {
            Elf32_Ehdr elfhdr;
            if (nbytes <= sizeof (Elf32_Ehdr))
                  return 0;


            u.l = 1;
            (void) memcpy(&elfhdr, buf, sizeof elfhdr);
            swap = (u.c[sizeof(int32_t) - 1] + 1) != elfhdr.e_ident[5];

            if (getu16(swap, elfhdr.e_type) == ET_CORE) {
#ifdef ELFCORE
                  if (dophn_core(ms, class, swap, fd,
                      (off_t)getu32(swap, elfhdr.e_phoff),
                      getu16(swap, elfhdr.e_phnum), 
                      (size_t)getu16(swap, elfhdr.e_phentsize)) == -1)
                        return -1;
#else
                  ;
#endif
            } else {
                  if (getu16(swap, elfhdr.e_type) == ET_EXEC) {
                        if (dophn_exec(ms, class, swap,
                            fd, (off_t)getu32(swap, elfhdr.e_phoff),
                            getu16(swap, elfhdr.e_phnum), 
                            (size_t)getu16(swap, elfhdr.e_phentsize))
                            == -1)
                              return -1;
                  }
                  if (doshn(ms, class, swap, fd,
                      (off_t)getu32(swap, elfhdr.e_shoff),
                      getu16(swap, elfhdr.e_shnum),
                      (size_t)getu16(swap, elfhdr.e_shentsize)) == -1)
                        return -1;
            }
            return 1;
      }

        if (class == ELFCLASS64) {
            Elf64_Ehdr elfhdr;
            if (nbytes <= sizeof (Elf64_Ehdr))
                  return 0;


            u.l = 1;
            (void) memcpy(&elfhdr, buf, sizeof elfhdr);
            swap = (u.c[sizeof(int32_t) - 1] + 1) != elfhdr.e_ident[5];

            if (getu16(swap, elfhdr.e_type) == ET_CORE) {
#ifdef ELFCORE
                  if (dophn_core(ms, class, swap, fd,
                      (off_t)elf_getu64(swap, elfhdr.e_phoff),
                      getu16(swap, elfhdr.e_phnum), 
                      (size_t)getu16(swap, elfhdr.e_phentsize)) == -1)
                        return -1;
#else
                  ;
#endif
            } else {
                  if (getu16(swap, elfhdr.e_type) == ET_EXEC) {
                        if (dophn_exec(ms, class, swap, fd,
                            (off_t)elf_getu64(swap, elfhdr.e_phoff),
                            getu16(swap, elfhdr.e_phnum), 
                            (size_t)getu16(swap, elfhdr.e_phentsize))
                            == -1)
                              return -1;
                  }
                  if (doshn(ms, class, swap, fd,
                      (off_t)elf_getu64(swap, elfhdr.e_shoff),
                      getu16(swap, elfhdr.e_shnum),
                      (size_t)getu16(swap, elfhdr.e_shentsize)) == -1)
                        return -1;
            }
            return 1;
      }
      return 0;
}
#endif

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